Self-contained die cushion with air saver



United States Patent O 3,456,938 SELF-CONTAINED Dit?. CUSHEON WITH AIR SAVER Thomas R. Hitch, Aidan, Pa., assigner to E. W. Bliss Company, Canton, hio, a corporation of Delaware Filed Aug. 22, 1967, Ser. No. 662,464 Int. Cl. Flf /00, 9/06 U.S. Cl. 267-1 9 Claims ABSTRACT OF THE DSCLOSURE A self-contained die cushion for use on a power press wherein the cushion chamber is divided into two portions with a iluid passageway interconnecting the two portions. A valve in the passageway provides selective control whereby iiuid may be introduced into the two chamber portions or Huid may be exhausted from one of the chamber portions while the other chamber portion is sealed thereby permitting the cushion to drop to its inoperative position.

The present invention relates to the art of self-contained die cushions, and more particularly to a self-contained die cushion having an air saver or reservoir incorporated therewith.

This invention is particularly applicable for use in a power press wherein depending rods are used to support a hold-down ring of a drawing die and it will be described with particular reference thereto; however, it is to be appreciated that the invention has much broader application and may be used in various other environments wherein a die cushion is required.

Many dies used within power presses incorporate holddown rings or other auxiliary elements which are controlled to a certain extent by a die cushion located below the bed of the power press. These die cushions take a variety of forms; however, the most common die cushion includes two telescoped sleeves within walls defining an internal cushion chamber filled with a compressible iluid which biases the upper sleeve, or pressure pad, in an upwardly direction. A plurality of rods extending downwardly from the die within the press rest upon the upper sleeve. These rods coact with movable elements within the die so that the sleeve is forced downwardly by the rods during the downward stroke of the press. The downward movement of the upper sleeve compresses the uid within the cushion chamber so that the rods are forced in an upward direction by the upper sleeve during the upward stroke of the power press. The volume of air or other compressible fluid Within the chamber of the die cushion is quite large to provide the necessary biasing action for the downwardly-extending rods.

When a die is to be repaired or replaced, the die cushion must be dropped to an inoperative position. One common way of accomplishing this is to exhaust most of the uid in the chamber of the die cushion. This presents a substantial diiliculty since a relatively long period of time is required to exhaust and then replace the large volume of fluid within the die cushion. In an effort to reduce the time for exhausting and lling the chamber of the die cushion, relatively large supply hoses have been employed. These are expensive and they do not substantially reduce the total time required to drop the die cushion to its inoperative position and then raise the die cushion back to its operative position. To overcome the disadvantages of this particular arrangement, it has been suggested that a fluid reservoir should be mounted adjacent the die cushion with a valve between the reservoir and the cushion. When the die cushion is to be dropped, the valve is opened to store uid within the reservoir. The valve is then closed so that the uid remains in the reservoir. To raise the die cushion, the valve is again opened which allows the ow of iluid back to the die cushion. Although this arrangement is satisfactory in some respects, it involves complex and expensive mechanical apparatus to accomplish the operation of the die cushion.

The disadvantages of the prior art die cushions are completely overcome by the present invention which is a completely new concept to the art of die cushions and includes a simplified structure which greatly reduces the required time for dropping the die cushion from its upward operative position to its lower inoperative position, and also reduces the time required to raise the cushion back to its operative position.

Thus, the primary object of the present invention is the provision of a self-contained die cushion which is inexpensive to produce, usuable in existing presses without modification, and easily and rapidly dropped into the inoperative position and raised to the operative position with a minimum of fluid.

Another object of the present invention is the provision of a self-contained die cushion which requires less air or fluid to shift from the inoperative position to the operative position than was heretofore required.

A further object of the present invention is the provision of a self-contained die cushion which incorporates two separate tluid compartments in the cushion chamber, both of which coact to provide the biasing action of the cushion and only one of which is exhausted to permit the cushion to drop to its inoperative position.

Still a further object of the invention is the provision of a self-contained die cushion which incorporates two separate Huid compartments in the cushion chamber, both of which coact to provide the biasing action of the cushion and only the first of which is exhausted to drop the cushion to its inoperative position with a valve internally of the die cushion sealing the second chamber while the rst chamber is being exhausted.

Another object of the invention is to provide a selfcontained die cushion which incorporates two separate fluid compartments in the cushion chamber, both of which coact to provide the biasing action of the cushion during its operation, but only the tirst of which need be filled with Huid to raise the cushion from its inoperative position to its operative position.

These objects, as well as others which will become more apparent upon a complete reading of the following description, are achieved in a self-contained die cushion which includes a movable operative member having an inoperative lower position and an operative upper position with a fluid means for biasing the member in the upper direction at least when the member is in the operative position. The fluid means includes a cushion chamber lled with a compressible fluid and means for dividing the chamber into first and second chamber portions. A fluid passage interconnects the two chamber portions. In accordance with this invention an inlet passage and an exhaust passage are formed in the die cushion with both passages being in communication with the interconnecting passage between the two chambers.

A valve is movably received in the tiuid passage and is selectively operative to place the two chamber portions, the inlet passage and the exhaust passage in fluid communication.

With this arrangement, a die cushion constructed in accordance with the invention provides a simple, inexpensive means whereby the rst and second chambers of the die cushion may be illed with fluid to lift the cushion to its operative position. During the filling operation, the valve is positioned so that the inlet passage in the die cushion is in lluid communication with the rst and second chamber portions. When the cushion is filled with fluid, the valve is rotated to isolate the charn ber from both the inlet and the exhaust passages while providing communication within the die cushion between the rst and second chambers, thereby permitting the two chambers to coact to bias the die cushion to its operative position. When it is desired to lower the cushion to its inoperative position, the valve need only be rotated to a third position in which the iirst chamber is in communication with the exhaust passage while the valve simultaneously seals the second chamber thereby retaining the fluid in the second chamber. The valve porting may be varied so that the rate of cushion descent may be controlled and it will be appreciated that, depending on the size of the valve ports and the degree to which the valve is opened, the cushion may be dropped very rapidly to its inoperative position. To raise the cushion back to its operative position, it is only necessary to rotate the valve to its original position with the only additional fluid required being the relatively small amount necessary to iill the one chamber that was exhausted. Thus, it is readily apparent that this arrangement provides an eliicient and relatively simple structure for saving a certain portion of the fluid within the die cushion between successive shifts in the condition of the cushion.

The objects and advantages above stated, as well as others which will be apparent to those having ordinary skill in the art, will best be understood from the following description used to illustrate the preferred embodiment of the invention when read in connection with the attached drawings in which like reference numerals indicate like parts in the various views:

FIGURE 1 is a partial cross-sectional side elevation view illustrating somewhat schematically the preferred embodiment of the present invention with the die cushio being filled with fluid;

FIGURE 2 is a view similar to FIGURE 1 illustrating the die cushion in its operating position;

FIGURE 3 is a view similar to FIGURES 1 and 2 illustrating the cushion in its inoperative position.

Referring now to the drawings wherein the showings are for the purpose of illustrating the preferred embodiment of the invention only and not for the purpose of limiting the same, there is illustrated a die cushion A constructed in accordance with the present invention. The die cushion A is mounted on a support plate B attached to the frame of a press bed in conventional manner. The general operation of the die cushion is well-known in the power press art and, accordingly, a further discussion of the press itself, except with regard to the general operation of the die cushion, is believed to be unnecessary.

The die cushion comprises a stationary, upwardly opening cylinder over which is telescopically received a movable sleeve or pressure pad 11. The pressure pad forms the operative member of the die cushion and includes an upper end wall 12,n the upper surface of which is adapted to contact the lower end of operating rods in a manner well-known in the power press art.

The lower portion of the cylinder 10 is provided with an end plate 14 which is secured by appropriate means to the support plate B. In addition, the cylinder 10 includes an upper plate 16 which is secured at the upper end of the cylinder to dene a uid chamber portion 18 within the interior of the cylinder 10. The plate 16 includes a central opening 20 and a counterbored portion 22 in which there is received an upstanding tube 30. The tube 30 includes a passageway 32 which is coaxial with the opening 20 and has a diameter substantially equal to the diameter of the opening 20. The tube 30 is received in a counterbored opening 24 in the end plate 14 as is apparent from FIGURE l. The tube 30 further includes a plurality of openings, orifices or ports 34 circumferentially spaced about the periphery of the tube providing communication between the passage 32 in the tribe and the chamber portion 18 in the cylinder 10.

The plate 16 also cooperates with the pressure pad 11 to define an upper chamber portion 40. This chamber portion combines with the lower chamber portion 18 to define a die cushion chamber which, when filled with Huid, provides the necessary upward bias against the pressure pad 11 to force the aforementioned rods in an upward direction, or to control the downward movement of these rods. As the press is operated, the compressible uid in chamber 18 of the cushion is freely in communication with the fluid in chamber 40 through the openings 34 in the passage 32.

An inlet passage 44 is formed in the end plate 14 with the inlet passage being aligned with an inlet port 45 in the tube 30. An exhaust passage 46 is also formed in the end plate with the exhaust passage being coaxial with an inlet port 47 in the tube 30. As illustrated in the drawings, the inlet passage has a larger diameter than the exhaust passage, but it will be appreciated that the relative dimensions of 'both passages may be varied to suit the particular circumstance.

To control the introduction and exhaustion of the fluid in the chambers 18 and 40 there is provided in the cushion a Valve assembly, indicated generally by the reference numeral 50. This valve assembly comprises a cylindrical sleeve 52 which has a central passage 54 opening upwardly of the sleeve and an inner end wall 55 which closes the lower end of the passage 54. The outer diameter of the sleeve 52 closely approximates the inner diameter of the passage 32 with the sleeve being rotatably received in the passage 32. Appropriate means may be employed for positioning the sleeve rotatably in the passage 32 adjacent the lower end thereof. The sleeve further includes a plurality of radial ports or orifices circumferentially and longitudinally spaced on the sleeve. These ports or orifices correspond to the ports in tube 30. Thus, the sleeve includes a plurality of circumferentially spaced radial ports 57 adjacent the upper end thereof with the ports being equal in diameter to the ports 34 in the tube 30. However, there are twice as many ports 57 as there are ports 34 since the ports 57 are adapted to be aligned with the ports 34 in two different positions of the valve 50 and non-aligned with the ports 34 when the valve is rotated to a third position. The valve further includes an inlet port 58 which is of a diameter corresponding to the diameter of the inlet passage 44. The inlet port 58 is aligned with the inlet passage 44 in one position of the valve 50 and out-of-alignment with the inlet passage when the valve is rotated to its two other positions. Circumferentially spaced from all of the other ports on valve 50 is an exhaust port 59 which is aligned with the exhaust passage 46 in one position of the valve.

An opening 62 is formed in the support plate B and an appropriate actuator for the valve 50 extends through the opening. It will be appreciated that the particular type of operator is but a matter of choice and may be manually, hydraulically, or electrically controlled.

Referring now to the operation of the die cushion A during nonmal operation of the cushion, the valve 50 is rotated to the position in which the inlet port 58 is aligned with the inlet passage 44 and fluid, preferably air, under pressure is introduced to the die cushion. Alignment of the inlet port 58 also aligns two of the ports 57 with the ports 34 in the tube 30. Thus, as air is introduced to the inlet passage, the air is free to circulate into the lower chamber 18, as well as through the passage 32 to the upper chamber 40. As the pressure increases in the chambers 18 and 40, the pressure pad 11 is moved to its operative position, as shown in FIGURE 1. When the operative position of the pressure pad has been achieved, the valve 50 is rotated to a position in which the inlet port 58 is no longer aligned with the inlet passage 44. In this position, the other of the ports 57 are aligned with ports 34 but the fluid in the Ichambers 118 and 40 is otherwise entrapped and provides a means of biasing the pressure pad to its operative position. During normal operation of the die cushion, the pressure pad 11 reciprocates a certain distance relative to the lower cylinder 10, due to the upward and downward movement of the press. This reciprocating movement compresses the air within the chambers 18 and 40 with the compressed air thereafter forcing the pressure pad in an upward direction as the press starts the upper portion of its cycle. This, then, is the general operation of the die cushion; however,`when the die is to rbe replaced or repaired it is necessary to drop the die cushion to a lower position.

In accordance with this invention, the die cushion is moved to its inoperative position quickly and easily simply by rotating the valve 50 to the position shown in FIGURE 3. In this position, the orifice 59 is aligned with the exhaust passage 46 and the inlet passage 44, as well as the ports 34, are blocked thereby providing communication between the chamber 40 and the exhaust passage 46. Under the weight of the pressure pad 11, the fluid in chamber 40 is exhausted to the atmosphere through the exhaust passage 46. The compressed fluid in the chamber 18 is prevented from escaping but due to the plate 16 the presence of the compressed fluid in chamber 18 does not inhibit the descent of the pressure pad 11. Ordinarily it is desirable to have the cushion in its lowest most point of reciprocation under the pressure of the slide before rotating the valve 50 to the position Vshown in FIGURE 3. In this manner, the maximum amount of fluid is forced into the chamber 18 thereby permitting the saving of additional iluid.

It will be appreciated that the rate of descent of the pressure pad 11 may be controlled by the degree to which the orifice 59 is aligned with the passage 46. Moreover, the cushion descent may also be controlled by varying the size of the orifice 59 and the exhaust passage 46. In this manner, it is possible to obtain either a rapid or a carefully controlled descent of the pressure pad.

To again render the die cushion operative, it is only necessary to rotate the valve 50 to its original position, shown in FIGURE l, wherein the inlet port 58 is aligned with the inlet passage 44. The fluid under pressure is then supplied to the die cushion with only a small amount of additional fluid pressure being required since the fluid previously trapped in the chamber 18 is now available to be utilized. Accordingly, only a relatively small volume of fluid is required to shift the pressure pad 11 back to its operative position.

From the foregoing description, it will be appreciated that the objects set forth have been fully achieved by the described die cushion. Thus, the chamber 18 functions as an air saver -or reservoir within the cushion itself thereby obviating the necessity for an external reservoir. Moreover, through the use of a simple valve and passage arrangement wholly internal of the die cushion it is possible to achieve both a rapid descent, as well as a controlled descent, of the pressure pad 11. In addition, the pressure pad may be moved back to its operative position with only a very small volume of additional fluid being required thus minimizing the time required to render the cushion operative. All of these advantages are achieved in a die cushion construction which does not require extensive modification or additional expensive equipment to be used in existing presses.

Although the present invention has been described in connection with but one structural embodiment, it is t0 be understood that various changes may be made in this embodiment.

Having thus described my invention, I claim:

1. In a self-contained die cushion including a movable, operative member having an inoperative lowered position and an operative upper position, a fluid means for biasing said member in an upward direction at least when said member is in the operative position, said fluid means including a cushion chamber adapted to be filled with a compressible fluid, means for dividing said chamber into first and second portions and a fluid passage providing communication between said portions, the improvement comprising:

an inlet passage communicating at its inner end with said iluid passage,

an exhaust passage communicating at its inner end with said fluid passage, and

valve means movable supported in said fluid passage,

said valve means being movable in said fluid passage to a plurality of operative positions whereby said inlet passage, said exhaust passage, and said chamber portions may be selectively placed in communication with each other.

2. The improvement of claim 1 wherein said cushion includes a stationary cylinder over which said movable member is telescopically received,

said chamber being defined by said stationary cylinder and said movable member,

said dividing means including a plate secured to said stationary cylinder, and

said iluid passage comprising a tube in an opening in said plate and a plurality of ports in the wall of said tube.

3. The improvement as defined in claim 2 wherein said valve is rotatably supported in said tube.

4. The improvement as defined in claim 1 wherein said valve comprises a rotatable cylinder having a central passage formed therein and ports in the wall of said cylinder communicating with said central passage,

one of said ports being adapted to be aligned with said inlet passage in one position of said valve and another of said ports being adapted to be aligned with said exhaust passage in another position of said valve.

5. The improvement as defined in claim 2 wherein said valve includes a fluid passage with ports adapted selectively to be aligned with said ports in said turbe,

said inlet passage being in communication with one of said ports in said tube and said exhaust passage being in communication with another of said ports in said tube.

6. The improvement as defined in claim 1 wherein said valve is supported in said fluid passage for movement between a first position wherein said inlet passage is in communication with said first and second chamber portionsa second position wherein said inlet passage and said eX- haust passage are isolated from said chamber portions and a third position wherein said exhaust passage is in communication only with one of said chamber portions.

7. The improvement as defined in claim 1 wherein said valve includes a passage therethrough, said valve being movable to a position wherein only said exhaust passage is in fluid communication through said valve passage with one of said chamber portions.

8. The improvement as defined in claim 1 wherein said die cushion includes a stationary cylinder over which said movable member is telescopically received,

plate means closing the one end of said stationary cylinder;

said dividing means comprising a plate carried by the other end of said stationary cylinder; said lluid passage comprising a stationary tube extending between said plate and said plate means with one end of said tube being received in an opening in said plate and the Iother end of said tube received in an opening in said plate means, a passage through said tube, a plurality of circumferentially and longitudinally spaced ports in the wall of said tube, f

said inlet and exhaust passages being formed in said plate means with one of said ports being in communication with said inlet passage and another of said ports being in communication with said exhaust passage.

9. The improvement as defined in claim 8| wherein said 7 8 valve means comprises a rotatable cylinder having a Cen- 3,013,791 12/ 1961 Gold 267-1 tral passage therein, 3,375,001 3/ 1968 Hennells 267-1 a plurality of ports dened in the wall of said cylinder; 3,379,430 4/ 1968 Hennells 267--1 said ports being selectively aligned with the ports in said tube to control the ow of uid between said chaml ARTHUR L, LA POINT, primary Examiner ber portions and said passages. Q

DANIEL F. WORTH, III, Asslstant Exammer References Cited US. CI. XR. UNITED STATES PATENTS 267 64 2,318,819 5/1943 Verson 267-1 In 

